Project Summary/Abstract: The biochemical and functional decline in the noradrenergic and dopaminergic systems is a distinct characteristic of aging, which contributes to locomotive, cognitive and mental alterations in aged individuals. Restoring the activity and function of these two systems is an important therapeutic strategy for aging. However, the corresponding therapeutic interference in these two systems is limited. Several studies have shown that an intact noradrenergic system and an increased level of endogenous norepinephrine contribute to the recovery of damaged dopaminergic neurons. These important findings indicate that manipulating to enhance noradrenergic activities may not only restore noradrenergic function, but also affect the function of the dopaminergic system. Interestingly, transcription factors, such as Phox2a, Phoa2b, Hand 2 and Gata3 expressed in noradrenergic neurons, play an important role in maintaining the noradrenergic phenotype and function in adult brains. Hence, we hypothesize that forced overexpression of these transcription factors in the locus coeruleus (LC) region of aged rat brains will effectively restore declining noradrenergic functions, which in turn will facilitate the functional improvement of impaired DA systems, an effect that will be mirrored by treatment of aged animals with drugs that increase noradrenergic transmission. To address this hypothesis, lentiviral constructs of the transcription factors Phox2a/2b, Hand2 and Gata3, either alone or in combination, will be microinjected into the LC region of aged rats. Pharmacologically manipulated groups will be concurrently treated with either norepinephrine precursor L-threo-3,4-dihydroxyphenylserine (L-DOPS), ?2- adrenoceptor antagonist, or ?2-adrenoceptor agonist. Relevant gene expression and neurotransmitter levels in the brain regions including the LC, striatum and hippocampus, as well as related behaviors, will be analyzed in these treated rats. Finally, a dopaminergic neuronal cell line, MN9D, will be used to explore the molecular mechanisms such as transactivation and chromatin remodeling underlying the facilitative effects induced by norepinephrine and the related neurotrophin on the dopaminergic phenotype. Thus at the conclusion of the proposed studies, supported by exciting preliminary data, we will be able to demonstrate that these manipulations will improve noradrenergic and dopaminergic functions in aged animals. This research will provide new insights into the regulatory roles of these transcription factors in central noradrenergic and dopaminergic phenotypes in aged animal brains, and will expand our understanding of the link between the LC- norepinephrine and dopamine systems during the progression of aging.